X-ray installation comprising a movable anode x-ray tube



Sept. 7, 1937 1 X-RAY INSTALLATION COMPRISING A MOVABLE *ANODE X-RAYTUBE BOUWERS Filed- Nqv. 22. 1934 INVENTOR ALBERT BOUWERS Patented Sept.7, 1937 UNITED STATES PATENT OFFICE X-ItAY INSTALLATION COMPRISING AMOVABLE ANODE X-RAY TUBE Albert Bouwers, Eindhoven,

Netherlands, as-

signor to N. V, Philips Gloeilampenfabrieken, Eindhoven, Netherlands 10Claims.

The present invention relates'to an X-ray installation and circuitstherefor, which installation comprises an X-ray tube having a movableanode, and to methods of operating such'installations. 7

My invention will be described in connection with a rotating anode typeof X-ray tube as described in my U. S. Patent No. 1,893,759, but is notlimited thereto. 1

In X-ray work, especially for taking instantaneous X-ray exposures, itis desirable, prior to taking the exposure, to radioscopically locatethe part to be radiographed. In the past, as a rule two individual tubesof different type and capacity were used for such purpose, the one forradioscopy being a small capacity and lower voltage tube, whereas forexposures, .a larger capacity, higher-voltage tube was used. For thesecond tube, especially for taking instantaneous radiographs requiring avery high instantaneous load,rotatable anode tubes were advantageouslyused.

The present invention relates to an installation in which instead of twoseparate tubes, a single tube is used for both the radioscopic Work andfor the exposure, the tube being of the rotatable anode type.

Rotatable anode tubes are comparatively expensive, and because of thehigh rotating speeds required for their use at the high instantaneousloads, and the difficulty of providing bearings within the high vacuumcontainer of the tube which can stand such speeds, the useful life ofsuch tubes is limited, even if lightly loaded, because of the gradualWearing of the bearings.

Thus, while such a tube could stand the high load required inradioscopic work without injury, 1

even for the prolonged times required for radioscopic work, thecorresponding prolonged rotation of the anode would very considerablyshorten the life of the tube. Thus, whatever advantage there might be inthe use of a single tube instead of two tubes is more than offset by thefact that for radioscopy a considerably more expensive tube than isrequired for such work is used up. I have found that a rotating anodetube can be advantageously used for both radioscopy and radiographywithout the radioscopic work markedly shortening the life of the tube.

According to the invention, the rotational speed of the anode forradioscopic work is considerably reduced below the value required forexposure work, or the anode may be kept altogether stationary duringradioscopy. Simultaneously with the changing of the rotational speed of.the anode for radioscopy and for exposure work, the voltage applied tothe tube, and the current passing through the tube (the latter forinstance by changing of the heating current of the cathode) aresimultaneously, preferably automatically, adjusted to meet therequirements of the respective type of work.

While by the proper dimensioning of the target surface, the specificpower applied to a stationary target portion during radioscopy will notbe ex- 10 cessive, nevertheless I prefer to rotate the anode at acomparatively low speed during the radioscopy, partly to provide a moreuniform wearing on the target during the radioscopic work, and partlybecause, the anode already having a slow rotation, it is possible toswitch over from radioscopic work to exposure work without much timedelay. As such small rotating speeds do not markedly affect thebearings, the rotation of the anode during radioscopy does not markedlyshorten the life of the tube. For instance, while in exposure work withsay 10 kw. the anode may have a speed of 2500 to 3000 R. P. M. and forvery high loads e. g. with 20 kw; a speedof even 5000 to 6000 R. P. M.,during radioscopy with 250 watts for example a very low speed may beused, for instance to 200 R. P. M. or even less.

In practicing my invention, as will be shown in some examples hereafterdescribed, the adjustments of the operating voltage, of the operatingcurrent (for instance by means of the heating current), and of the speedof rotation, are done simultaneously and automatically (orsemi-automatically) so that the establishing of the proper operatingconditions for either radioscopy or for taking the exposures areobtained by the operation of a single switch or button. The varyingadjustments are thereby preferably effected by a single multiple contactswitching device having two positions, one for radioscopy and the other40 for radiography.

The variations in the speed of rotation of the anode may be eifected invarious manners, for instance the stator may be supplied with difierentvoltages or the frequency of the alternating current supplied to thestator may be changed. A simple manner of changing the speed is by meansof an impedance in the circuit of the I stator current, which, forradioscopy, sufficiently reduces the current and thus the torque, as torotate the anode at the desired low speed. This impedance can be thenshort-circuited for exposure work, permitting the anode to rotate at itshigh speed.

Various other novel features of my invention will appear as thespecification progresses:

In order that my invention may be clearly understood and readily carriedinto effect, I shall describe same more fully with. reference to theaccompanying drawing, in which:

Figure 1 is a schematic wiring diagram in which the operating voltage ofthe X-ray tube is supplied from a transformer.

Fig. 2 is a schematic wiring diagram in which the operating voltage ofthe X-ray tube is supplied by condensers during the exposure.

Referring to Figure l, the X-ray tube I has its rotary anode 2 and itscathode 3 connected rer spectively to the two ends of the secondarywinding 4 of a high-tension transformer I00 having a primary winding 5,and the cathode 3 is also connected across the secondary winding of aheating transformer 3i.

To establish the necessary circuits for the operating current and theheating current of the X-ray tube, and for the rotation of the anode,for the conditions required for radioscopy and for taking the exposurerespectively, there is provided a two-position multiple contact switch9, which is spring-biased in its lower position by spring 95 andelectromagnetically raised into its upper position by actuating coil 13which acts on a plunger rod.

As shown in the drawing, the plunger rod of the switch 9 is providedwith five contact arms Hill, :83, I64, Hi5 and I96, insulated from eachother and adapt-ed to connect contact pairs 'l'2 i, 8I0, 2 !25, 262'Iand 3839 respectively. When the switch is in its lower position, whichis the position for radioscopy, the contact arms I03 and ms bridge theirrespective contact pairs and the remaining contact arms are open, whereas when the switch 9 is in its upper position, which is the position fortaking the exposure, the contact arms I02, I04 and I06 bridge theirrespective contact pairs and the arms I93 and I05 are open.

For rotating the anode 2, a three-phase stator 33 is provided, and forsupplying a three-phase current to the stator from a single-phase supply55, a current supply device 34 is provided, which device may be atransformer or a frequency alternator; such constructions being wellknown need not be shown in detail.

To use the X-ray tube for radioscopy, the switch 56 is first closed,which causes the anode to rotate by energizing the device 34 from thesupply I5 through a circuit including the conductors IT, 32 and 36,adjustable resistance .i'l', device 36, conductors 35 and 29, back tothe other pole of the switch it. The adjustable resistance 3? can beadjusted so that the anode 2 will rotate at a slow speed during theradioscopy.

The heating of the cathode 3 is effected by energizing the transformer3! from alternating network I5 through a circuit passing through onepole of switch I6, conductors 2E) and I9, contact point 26, contact armI65, contact point 21, fixed resistance 29, adjustable resistance 30,primary winding of heating transformer 3i, and back through conductors32 and ii to the other pole of the switch I6. The adjustable resistance30 regulates the current through the incandescent cathode to the desiredvalue for the radioscopy.

When the anode 2 is thus rotated at a slow speed and the heating currentis supplied to the incandescent cathode, the operating voltage requiredis applied to the tube by energizing the primary winding 5 ofhigh-tension transformer Iiiil from autotransformer 6, as follows:

The autotransformer 6 is fixedly connected with one of its ends H to oneend of the winding 5, this junction point being also connected to onepole of the switch it. The other pole of switch it is connected throughconductors I! to a fixed tap H of the autotransformer 6. Beyond the tap9! the autotransformer 8 is provided with a plurality of taps formingtwo groups, the first group,

cooperates with a voltage regulating device I2 having a movable contactarm ill by means of which successive taps of the transformer can beconnected to a conductor I 29. Autotransforrner 6 is also provided withadditional taps Which possibly together with some of the upper taps alsocooperating with arm I2--cooperate with a contact arm 23 of a voltageregulator 23.

To energize the winding 5 (the switch It having been closed for therotation of the anode and the heating of the cathode, as well as theenergization of the autotransformer 6) a hand switch ii is closed,establishing the energizing circuit of the winding 5 as follows:

From the energized autctransformer 6 through winding 5, conductor $22,contact 8, contact arm 2B3, contact ill, closed switch H, conductor I23,contact arm I2 and corresponding tap of autotransformer 6. By varyingthe position of contact arm I2 a smaller or larger voltage can beapplied to the winding 5 and thus a smaller or larger voltage is appliedto the X-ray tube.

To use the tube for taking an exposure a hand switch It is closed, whichenergizes the coil l3 of switch 9 through a circuit passing through onepole of switch It, conductors 20, I3 and 92, coil I3, switch M,conductors I8 and I1, back to the other pole of switch IS. The switch 9being thus raised against the tension of spring 99 into its upperposition, breaks connections at contact arms 33 and I05 and establishesconnections at contact arms )2, I94 and IE6.

With the switch 9 in this position the anode 2 is caused to rotate at ahigher speed as resistance 31 is short-circuitcd by contact arm I66 andconductor iii), and thereby the full supply voltage is applied acrossthe device 34.

The heating current is increased through the heating transformer 3| andadjusted to a value suitable for taking the exposure by interrupting itscircuit through the higher resistance series combination of fixedresistor 29 and adjustable resistor 35] and establishing its circuitthrough a lower resistance adjustable resistor 28.

This circuit can be traced as follows: From one pole of switch I6,conductors Bi! and I9, contact 24, contact arm I8 5, contact 25,adjustable resistance 28, primary winding of heating transformer 3!,conductors 32 and El back to the other side of supply 85. The adjustableresistance 23 serves to adjust the heating current of cathode 3 to itsproper value for taking the exposure.

The apparatus is now in condition for taking an exposure as the anode isrotating at high speed and cathode 3 is being supplied with the properheating current for this purpose.

The application, of the operating voltage of the tube for the exposureis initiated and terminated by a time switch 22, which also regulatesthe time of exposure.

The energizing circuit of the high voltage transformer winding 5 isestablished by the actuation of the handle 22, which in its normalinactive position intercepts this circuit. This energizing circuit canbe traced as follows: From end MI of autotransformer 6 through winding5, conductor I22, contact I, contact arm I02, contact 2|, time-switch22, arm 23 of voltage regulator 5 23, to the selected tap o1autotransformer B.

Adjustment of device 2% permits decrease or increase of the voltageapplied to primary winding 5, and thus across the X-ray tube for theexposure.

0 At the end of the selected exposure time the time-switch 22, in knownmanner, interrupts the energizing circuit of primary winding 5, afterwhich by opening. switch l4 the apparatus can be returned to its propercondition for radioscopy.

Fig. 2 shows a modification of the arrangement shown in Figure 1,similar parts being designated by similar reference numerals. In themodification of Fig. 2 the operating current of the tube during theexposure is obtained by utilizing the discharge current of previouslycharged condensers. Also the timing of the exposure is obtained withouta time switch.

Similarly to Figure l, a multiple contact switch 53 is provided toestablish the desired circuits for the operating current and heatingcurrent of the X-ray tube, and for the rotation of the anode for theconditions required for radioscopy, and for taking the exposurerespectively. Switch 53 is a two-position switch, being, as shown,biased in its right-hand position by a tension spring 911 and beingmoved into its left-hand position by an actuating magnet coil 6i, actingon a plunger rod which carries contact arms Hi3, H5, H2, H3 and I I4,which arms are insulated from each other and are adapted to connectcontact pairs 65-61, IE-13, 5554, E i--15, and 6554 respectively.

When the switch is in its right-hand position, which is the position forradioscopy, contact arm H2 bridges its respective contacts, and all ofthe 0 other contact arms are open, and when the switch is in itsleft-hand position, which is the position for taking the exposure,contact arms Ilii, ill, I I3 and i M bridge their respective contacts,while contact arm I I2 is open. The three-phase stator 5 33 and controldevice 353 are assumed to be similar to those of Figure 1.

The operating current of the X-ray tube isobtainedfrom the condenserbattery consisting of two series-connected condensers 5i and 52. 0 Thecondensers 5i and 52 are first charged through separate rectifiers and43 by comp-lementary halfwaves of the alternating cur rent supplied fromcommon high-tension transformer H5. The rectifiers A5 and 48 are shownas being cathode rectifier tubes having anodes 46 and 58, and cathodes it and 411 respectively. One end of the cathode 3 of X-ray tube I is connected to the anode 5i and to one terminal of condenser 5!, the otherterminal of condenser .0 iii being connected to the end 93 of secondarywinding 49 of high-voltage transformer 5 l5 having a primary winding 32.To the other end of secondary winding 49 is connected the anode 46 andone end of the cathode ll, the other end of cathode 4? being connectedto a tap H6 of the Y winding 49 for the supply of its heating current.The anode 2 of the X-ray tube i is connected through the switch memberH, for example a 0 switch as isdescribed in U. S. Patent 1,946,324, of

an electromagnetic switch 95-having an actuating coil Mi-to the end 5541of the cathode M, and also to one terminal of condenser 52. The otherterminal of condenser 52 is connected to the end 5 93 of secondarywinding 49. Across the ends of back through the other pole of switch It.

causes switch 53 to move against tension of 7 spring 98 into itsleft-hand position, whereby g:

cathode 3 is connected the secondary winding of heating transformer 3|.

With the apparatus in the position shown, all of the parts arecurrentless, and if it is desired to use the tube for radioscopy, firstthe main switch l6 and then a hand switch 4! are closed. Upon closure ofswitch A! the primary winding 42 is energized, as well as the primarywinding of transformer 43, from the current supply source E5. Thesecondary winding of transformer 43 supplies heating current to cathodeM and also energizes coil 59 of a time delay switch 96. Energization oftransformer H5 causes the heating of cathode 4'! and also applies acrossthe X-ray tube 5 the operating voltage required for radios copy, as theswitch member H is closed due to its coil "it being de-energized.

The device 34 is only slightly energized as the contact arm H3 is in itsopen position and the current to the device 34 must pass through animpedance Ti, and conductor 62 from the source 55; the other side ofdevice 34 being connected through conductor 63 and closed time contact58 to the other pole of source 55. Thus the anode 2 rotates at a slowspeed during radioscopy, which not only conserves the bearings but alsomaintains the advantage of anode rotation.

The closure of contact 58 also energizes the heating transformer 31 fromthe supply source l5 through a circuit passing through one pole ofswitch 56, contact 58, conductor 51, primary winding of transformer 31,fixed resistance 29, variableresistance 30, contact 54, contact arm H2,contact 55, conductor 56, back to the other pole of switch it. serves toregulate the heating current of cathode 3 to its proper value requiredfor the radioscopy.

Thus for radioscopy, the anode 2 is rotated at a slow speed, theincandescent cathode 3 is heated to the proper value desired forradioscopy, and the proper operating voltage of the tube is suppliedfrom the secondary winding is.

To take an exposure a push button 60 is closed, which energizes coil 61of switch 53 from the supply !5 through the following circuit: Throughone pole of switch it, conductor 62, push button 58, coil iii, conductor(it, closed contact 58, and This contact arm H4 shunts push button 69,which retains the coil BI energized even if the button 6%! is released.

With the switch 58 in its left-hand position contact arm Iii) bridgescontacts ii! and 66 and energizes coil ill of switch 55 from thesecondary winding of transformer at through the following circuit:conductor 68, contact 656, contact arm llil, contact El, conductor 69,coil H3, and back to the other side of the secondary winding oftransformer 43.

Opening of switch ll interrupts the operating circuit of the X-ray tube.Thereby the condensers 5i and 52 are charged up at a rate depending onthe constants in their charging circuits and to a voltage approximatingthe maximum voltage existing at the terminals of the secondary winding49.

The movement of switch 53 into its left-hand position also removes theresistances 29 and 30 from the energizing circuit of transformer 3| bydisconnecting points 55 and 5d due to the opening of contact arm H2, andestablishes the energizing circuit of this transformer throughresistance 28 by bridging contacts 72 and 73 The variable resistance 30through contact arm I II. The heating current is thereby increased andcan be adjusted to the proper value required for the exposure, byadjusting resistance 28.

The connection through contact arm HE! is established prior to theclosure of the heating current circuit through contact arm Iii, so thatthe contact at El! is interrupted before the contact arm Hi touchescontacts ":12 and l3. The current through coil ll! must remain flowingduring the further movement of switch 53 and for this purpose contactarm H is designed to keep contacts 66 and iii connected. This has beenindicated in the drawing by a small line at each end of the contact arm.Contact arm H4 is of the same shape in order to prevent that switch 53is drawn backward by spring 95] when the push button St is releasedbefore switch 53 has reached its left-hand position.

The switch 53 is provided with a time delay in its movement from rightto left to establish a time interval between the interruption of theenergizing circuit of the cathode 3 through contact arm H2 and there-establishing of this energizing circuit through contact arm Hi;thereby the cathode will be permitted to cool down before switch 95 isopened and thus switch 95 will not be required to interrupt a current inthe high tension anode circuit.

The closure of contact arm H3 causes the full supply voltage of thenetwork i5 to be applied to the device 3Q through the following circuit:Through one pole of switch it, conductor 62, contact "M, contact arm H3,contact 15, conductor l6, device 34, conductor t3, contact 58, backthrough the other pole of switch It. The anode 2 is thus caused torotate at the desired high speed.

The above establishes the proper conditions for taking the exposure. Totake the exposure, switch 4! is opened, which de-energizes transformersH5 and 43. De-energization of transformer H5 interrupts further chargingof condensers BI and and also the heating of cathode 4'! of rectifiertube 43. De-energization of transformer 63 causes de-energization ofcoils l8 and 5% and of the cathode id of rectifier tube 55.

The de-energization of the cathodes of rectifiers 45 and 48 interruptsthe circuits through same, whereas deenergization of coil 16 permits theclosure of contact member H, thus establishing a discharge circuit forcondensers 5i and 52 through the X-ray tube l.

The de-energization of coil 59 ultimately breaks the circuit of device 3and the heating circuit of the cathode 3 and thus causing the stoppageof the rotation of the anode after the exposure has been completed.

What I claim is:

1. An X-ray installation comprising an Y-ray tube having a movableanode, an electric power supply system for said tube comprising a sourceof power and adjusting means to adjust the amount of power supplied tothe tube, a second electric system for moving said anode comprisingcontrol means to control the rate of movement thereof, and means forinterlocking said adjusting means and said control means to causesimultaneous operation thereof and to cause the anode to move a higherrate for a larger amount of power supplied to the tube and to move at alower rate for smaller amount of power supplied to the tube.

2. An X-ray installation comprising an X-ray tube having a rotatableanode, an electric power supply system for said tube comprising a sourceof power and adjusting means to adjust the amount of power supplied tothe tube, a second electric system for rotating said anode, comprisingcontrol means to control the rotational speed of the anode, and meansfor interlocking said adjusting means and said control means to causesimultaneous operation thereof and to cause the rotational speed of theanode to be higher for a larger amount of power supplied to the tube andlower for a smaller amount of power supplied to the tube.

3. An X-ray installation comprising an X-ray tube having a rotatableanode, an electric supply system for said tube comprising a source ofpower and adjusting means to adjust the operating current and operatingvoltage of the X-ray tube to values suitable for radiography and tovalues suitable for radioscopy, a second electric system for rotatingsaid anode comprising control means to control the rotational speed ofthe anode to a high value and to a low value, and switching meansconnected with said adjusting means and said control means to cause therotational speed of the anode to have the low value when the operatingcurrent and voltage of the X-ray tubes are adjusted to the radioscopicvalues, and to have the high value when the operating current andvoltage of the tube are adjusted to the radiographic values.

4. An X-ray installation comprising an X-ray tube having anincandescible cathode and a rotatable anode, an electric system forrotating said anode comprising an electromagnetic stator and a devicefor energizing said stator, an electric power supply system for saidtube comprising means for energizing said cathode and means for applyingan electromotive force across said anode and cathode, and a two-positionswitching device having a set of contacts for controlling saidenergizing means and said means for applying electromotive force, and asecond set of contacts for controlling said device, said switchingdevice in one position conditioning said electric power supply systemfor supplying the power required for radioscopic work and conditioningsaid device to give the rotational speed of said anode a low value, andin its second position conditioning said electric power supply systemfor supplying the power required for radiographic exposures andconditioning said device to give the rotational speed of the anode ahigh value.

5. In an X-ray installation for making fluoroscopic examinations andradiographic exposures with a single X-ray tube having a rotatableanode, a two-position switching device for controlling the operatingcurrent to the tube and the rotational speed of the anode, said devicecomprising a set of contacts which when closed conduct current forradioscopic examination and for slowly rotating the anode, and a secondset of contacts which when closed conduct current for radiographicexposures and for rapidly rotating the anode, one set of contacts beingclosed in each position of the device.

6. An X-ray installation comprising an X-ray tube having anincandescible cathode and a rotatable anode, an electric system forsupplying power to said tube comprising means for applying anelectromotive force across said anode and cathode, and means forenergizing said cathode, said energizing means comprising a transformerhaving a secondary winding connected across said cathode and a primarywinding, and an electric circuit including said secondary winding, tworesistances, a stator for rotating said anode and a second electricsupply system connected therewith to provide for a high speed ofrotation and a low speed of rotation of said anode, and a two-positionswitching device which in one position establishes in said second supplysystem the conditions for providing the higher speed of rotation andconnects one of said resistances in said circuit, and in its otherposition establishes in said second supply system the conditions forproviding for the lower speed of rotation and connects the other of saidresistances in said circuit.

7. An X-ray installation comprising an X-ray tube having anincandescible cathode and a rotatable anode, an electric system forsupplying power to said X-ray tube including a heating currenttransformer having a secondary winding connected across said cathode anda primary winding, a second electric system for rotating said anodecomprising an electromagnetic stator, leads for supplying electriccurrent to said stator and an impedance in one of said leads, aresistance, a second resistance having a considerably lower value thansaid first resistance, and a twoposition multi-contact switching device,said device in one position connecting said first resistance in serieswith said primary winding, said device in its other position connectingin place of said first resistance said second resistance in series withsaid primary winding and short-circuiting said impedance. 7

8. In an X-ray installation for making radioscopic examinations andradiographic exposures with a single X-ray tube having a rotatableanode, an electric system for rotating said anode comprising anelectromagnetic stator, means for supplying power to the stator, andmeans to automatically change the amount of power supplied to the statorin accordance with the power supplied to the tube so that the anoderotates at about 100 R. P. M. during radioscopy and at several thousandR. P. M. during radiography.

9. In an X-ray installation comprising a rotatable anode X-ray tube, anelectric system for rotating said anode comprising an electromagneticstator, an alternating current supply for said stator to produce arevolving flux and a corresponding rotational speed of said anode, afrequency alternating device connected to said stator for changing therate of revolution of the flux and the rotational speed of the anode,means to adjust the amount of power supplied to the tube to a low valuefor radioscopy and to a high value for radiography, and meanscooperating with said adjusting means to vary the amount of powersupplied to said device to cause the anode to rotateat a high speedduring radiography and at a relatively low speed during radioscopy.

10. An X-ray installation comprising an X-ray tube having a movableanode, an electric power supply system for said tube comprising a sourceof power and adjusting means to adjust the power input to the tube to ahigh value suitable for radiography and to a low value suitable forfiuoroscopy, said low value being less than the permissible input to thetube with said anode stationary, and a second electric system for movingsaid anode at a high speed during the application of said high inputincluding means to maintain the speed of the anode at a low value duringapplication of the low power input.

ALBERT BOUWERS.

